Bonding Flashcards
Define an ion and how they are formed?
An atom or molecule with a net charge
Formed via gain or loss of electrons
Oxidation or reduction
What charge are cations and anions?
Cations are positive
Anions are negative
How does a molecular ion form?
When groups of 2 or more atoms are covalently bonded and they gain or lose an electron.
The charge is shared across the entire molecule.
Give some examples of molecular ions.
NH4^+
OH^-
NO3^-
CO3^2-
SO4^2-
What are ionic compounds?
Compounds composed of oppositely charged ions.
Overall charge is neutral as the ions cancel out.
What is an ionic bond?
An electrostatic force of attraction between two oppositely charged ions
How are ionic bonds formed?
Generally between metals and non metals
Elements seek to gain a full outer shell and therefore will donate electrons to enable both atoms to have a full electron arrangement.
What are the structures of ionic compounds?
Exist as giant ionic lattices where each ion is surrounded by oppositely charged ions (3D lattice)
Give some properties of ionic substances.
High melting and boiling points- due to strong electrostatic forces of attraction and therefore lots of energy is required to break them.
Ionic substances are soluble in polar solvents- polar bonds are unequally shared and therefore have slight charges meaning that the lattice can be disrupted.
Conduct electricity- but only when dissolved or molten as the ions are free to move.
What is a covalent bond?
Strong electrostatic attraction between a shared pair of electrons and the nucleus of the bonded atoms.
Usually occurs between two non metals
Cl-Cl
Can have single double or triple covalent bonds
(C-C. O=O. N triple bonded to N
What is a dative covalent bond? (Coordinate bond)
Where one atom donates both the electrons in a covalent bond.
What types of structures do covalent bonds produce?
Simple covalent molecules:(molecular)
Made up of small simple molecules existing as a lattice in solid state. Each of the atoms are tightly held together by covalent bonds.
Giant covalent molecules:(macromolecular)
Atoms are joined to adjacent atoms by strong covalent bonds forming a network (giant lattice)
-eg diamond/graphite/ silicon dioxide
What are the properties of simple covalent molecules?
Low melting and boiling points due to weak intermolecular forces of attractions between the molecules so a small amount of energy is required in order to disrupt the forces.
Soluble in non polar solvents (like dissolves like)
Non conductors as they have no feee charged particles
What are the properties of giant covalent molecules?
High melting and boiling points due to strong covalent bonds requiring lots of energy to break the bonds between the atoms.
Insoluble in both polar and non polar solvents as the covalent bonds are not disrupted by either solvent.
Non conductors except graphite as between the layers of the lattice are delocalised electrons which are able to move and therefore when a voltage I applied it can carry a charge.
What are the main intermolecular forces?
Hydrogen bonds,
Van der waals
Dipole- dipole Forces
What is a crystal?
Solid with a regular arrangement of atoms held together by forces of attractions (ionic, covalent, metallic) and intermolecular forces
What is metallic bonding?
Bonding between metals held together by strong electrostatic attraction between positively charged ions and negatively charged electrons.
What is the structure like in a metal?
Metals have a giant metallic structure with a fixed lattice of positive ions and a sea of delocalised electrons surrounding it.
(Electrons are free to move)
What are some properties of metals?
Electrical conductors- delocalised electrons can carry a current as they are free to move.
High melting and boiling points due to lots of energy being required to break the strong forces of attraction between the positive metal ion and negative electron.
Malleable and so can be bent or hammered into shape
Ductile- metals can be drawn out or stretched.
Define electronegativity
A measure of the tendency of an atom to attract a bonding pair of electrons in a covalent bond.
What trends are seen in electronegativity
Electronegativity increases across a period
Electronegativity decreases down a group
Explain the trending electronegativity across a period.
Electronegativity increases:
The charge on the nucleus increases as there is a greater number of protons and therefore a greater attraction for the outer electrons.
Therefore he bonding pair of electrons are attracted more strongly.
Explain the trend in electronegativity down a group.
Electronegativity decreases:
The bonding pair of electrons is further away from the central nucleus due to an increase in the number of electron shells.
Therefore there is less attraction between the nucleus and the electrons so the bonding pair of electrons is attracted less.
What are polar bonds?
When an electronegative atom is bonded to a less electronegative atom and and there is an uneven sharing in the bonding pair of electrons.
H-Cl
This forms permanent dipoles as there is a constant charge difference
What are non polar bonds?
If the two bonding atoms are identical then their attraction for the shared pair of electrons is equal. This means the electrons are equally distributed between the finding atoms.
Leads to a perfectly covalent bond.
Define electron density
The probability of finding an electron at a particular position in space
Why is CO2 non polar even though the molecule contains polar bonds?
The symmetry of polar bonds can cancel out the effect of any permanent dipole and so no difference in charge exists across the molecule hence the molecule is non polar.
What are intramolecular forces?
Interactions that act between atoms within molecules so they are held together by chemical bonds
What are intermolecular forces?
Interactions that act between molecules
Do not involve the transfer of electrons
What are van der waals forces?
Short range electrostatic forces of attraction between uncharged molecules.
What are permanent dipoles?
Occur when two atoms in a molecule have high differences in electronegativity and therefore the electrons are not shared evenly in a covalent bond.
Permanent dipoles are polar molecules.
What are induced dipole - dipole forces?
When a dipole is induced in a neighbouring molecule due to the random movements of electrons creating uneven distribution and hence a slightly polar molecule
What are hydrogen bonds?
The strongest intermolecular forces of attraction which occur between an electron deficient hydrogen which I is bonded to an electron negative element
(N O F)
And a lone pair of electrons.
Require the most energy to overcome
